This indicates a potential cross-site scripting attack.
Cross-site scripting (XSS) is a popular web security issue. If a web application doesn't properly validate input from one user and uses it in the output for other users, attackers can exploit it to send malicious code to other users.
All web application environments are susceptible to cross-site scripting.
Remote attackers can execute arbitrary code or gain sensitive information.
Review the code of web application and check all places where user input could possibly become part of the output for other users.